feat(skill): add codex target subcommand for skill install

docs/usage.md

@@ -28,14 +28,16 @@ printf '%s' 'Which task should I tackle first?' | jevwise decide --stdin \
 
 ```sh
 jevwise skill          # Default: .agent/skills/typesafe-ai/SKILL.md
-jevwise skill --agent  # Explicit default target
-jevwise skill --claude # .claude/skills/typesafe-ai/SKILL.md
-jevwise skill --force  # Replace an existing regular skill file
+jevwise skill agent   # Explicit default target
+jevwise skill codex   # .agents/skills/typesafe-ai/SKILL.md
+jevwise skill claude  # .claude/skills/typesafe-ai/SKILL.md
+jevwise skill codex --force # Replace an existing regular Codex skill file
 jevwise skill --online # Print the upstream GitHub URL only
 ```
 
 - Downloads the latest [upstream skill](https://github.com/typesafe-ai/skills/blob/main/skills/typesafe-ai/SKILL.md) unchanged, relative to the current project directory.
-- Local installation is the default; `--local` selects it explicitly. `--online` and `--local`, or `--agent` and `--claude`, cannot be combined. Online mode rejects installation flags and performs no download or write.
+- Local installation is the default; `--local` selects it explicitly. `--online` and `--local` cannot be combined. Online mode rejects target subcommands and installation flags and performs no download or write. Legacy `--agent`/`--claude` still work but are hidden from help; do not combine them with target subcommands.
+- Codex uses the [official project skill location](https://learn.chatgpt.com/docs/build-skills#where-codex-loads-local-skills), `.agents/skills`. The generic `agent` target retains the legacy singular `.agent/skills`; these are separate directories.
 - Hidden `--jev` selects the only supported skill. No decision credentials/configuration are read or sent. `--timeout` sets a `10s` default deadline for fetching and checks before file publication; filesystem calls are not forcibly interrupted.
 - Downloads require HTTP 200 and valid UTF-8 Markdown/front matter, are limited to 1 MiB, and never follow redirects. Invalid downloads leave existing skills untouched.
 - Existing files require `--force`. Static symlinks and nonregular destinations are refused; staging files are cleaned and complete bytes published without truncating the old inode.

internal/cli/skill.go

@@ -105,11 +105,14 @@ func newSkill(fetch skillFetch, install skillInstall) *cobra.Command {
 			if flag := cmd.Flags().Lookup("provider"); flag != nil && flag.Changed && flag.Value.String() != "jev" {
 				return errors.New("skill supports only the Jev provider")
 			}
+			if cmd.Name() != "skill" && (cmd.Flags().Changed("agent") || cmd.Flags().Changed("claude")) {
+				return errors.New("do not combine skill target subcommands with target flags")
+			}
 			if cmd.Flags().Changed("agent") && !agent || cmd.Flags().Changed("claude") && !claude || agent && claude {
 				return errors.New("select at most one enabled skill target")
 			}
 			if online {
-				if cmd.Flags().Changed("agent") || cmd.Flags().Changed("claude") || cmd.Flags().Changed("force") {
+				if cmd.Name() != "skill" || cmd.Flags().Changed("agent") || cmd.Flags().Changed("claude") || cmd.Flags().Changed("force") {
 					return errors.New("online skill mode does not accept target or force flags")
 				}
 				if _, err := fmt.Fprintln(cmd.OutOrStdout(), skillURL); err != nil {
@@ -145,8 +148,10 @@ func newSkill(fetch skillFetch, install skillInstall) *cobra.Command {
 				return err
 			}
 			target := ".agent"
-			if claude {
+			if claude || cmd.Name() == "claude" {
 				target = ".claude"
+			} else if cmd.Name() == "codex" {
+				target = ".agents"
 			}
 			if err := install(ctx, data, target, force); err != nil {
 				if errors.Is(err, errSkillExists) {
@@ -156,12 +161,17 @@ func newSkill(fetch skillFetch, install skillInstall) *cobra.Command {
 			}
 			return ctx.Err()
 		}}
-	cmd.Flags().BoolVar(&online, "online", false, "Print the upstream GitHub URL without downloading")
-	cmd.Flags().BoolVar(&local, "local", false, "Fetch and install the skill (default)")
-	cmd.Flags().BoolVar(&agent, "agent", false, "Install under .agent/skills (default)")
-	cmd.Flags().BoolVar(&claude, "claude", false, "Install under .claude/skills")
-	cmd.Flags().BoolVar(&force, "force", false, "Replace an existing regular skill file")
-	cmd.Flags().BoolVar(&jev, "jev", true, "Use the Jev skill")
-	_ = cmd.Flags().MarkHidden("jev")
+	cmd.PersistentFlags().BoolVar(&online, "online", false, "Print the upstream GitHub URL without downloading")
+	cmd.PersistentFlags().BoolVar(&local, "local", false, "Fetch and install the skill (default)")
+	cmd.PersistentFlags().BoolVar(&agent, "agent", false, "Install under .agent/skills (default)")
+	cmd.PersistentFlags().BoolVar(&claude, "claude", false, "Install under .claude/skills")
+	cmd.PersistentFlags().BoolVar(&force, "force", false, "Replace an existing regular skill file")
+	cmd.PersistentFlags().BoolVar(&jev, "jev", true, "Use the Jev skill")
+	for _, name := range []string{"jev", "agent", "claude"} {
+		_ = cmd.PersistentFlags().MarkHidden(name)
+	}
+	for _, target := range []string{"codex", "claude", "agent"} {
+		cmd.AddCommand(&cobra.Command{Use: target, Short: "Install Jev's skill for " + target, Args: cmd.Args, RunE: cmd.RunE})
+	}
 	return cmd
 }

internal/cli/skill_install.go

@@ -43,8 +43,8 @@ func installSkillAt(ctx context.Context, project string, data []byte, target str
 	if err := validateSkill(data); err != nil {
 		return err
 	}
-	if target != ".agent" && target != ".claude" {
-		return errors.New("skill target must be .agent or .claude")
+	if target != ".agent" && target != ".claude" && target != ".agents" {
+		return errors.New("skill target must be .agent, .agents or .claude")
 	}
 	switch runtime.GOOS {
 	case "js", "wasip1", "plan9":

internal/cli/skill_install_test.go

@@ -22,7 +22,7 @@ func skillInstalled(t *testing.T, project, target string, want []byte) {
 }
 
 func TestSkillInstallTargetsAndForce(t *testing.T) {
-	for _, target := range []string{".agent", ".claude"} {
+	for _, target := range []string{".agent", ".agents", ".claude"} {
 		project := t.TempDir()
 		if err := installSkillAt(context.Background(), project, validSkill, target, false, skillInstallHooks{}); err != nil {
 			t.Fatal(err)

internal/cli/skill_test.go

@@ -134,7 +134,7 @@ func TestSkillModesHelpAndLocalCallbacks(t *testing.T) {
 		t.Fatal("online mode used IO/config", err)
 	}
 	out, _, err = execute(skillRoot(nil, nil), "skill", "--help")
-	if err != nil || strings.Contains(out, "--jev") || !strings.Contains(out, "--online") {
+	if err != nil || strings.Contains(out, "--jev") || strings.Contains(out, "--claude") || strings.Contains(out, "--agent") || !strings.Contains(out, "codex") || !strings.Contains(out, "--online") {
 		t.Fatal("hidden Jev/help invalid", err)
 	}
 	for _, args := range [][]string{{"skill", "private-content"}, {"skill", "--online", "--local"}, {"skill", "--online=false"}, {"skill", "--local=false"}, {"skill", "--jev=false"}, {"skill", "--online", "--provider", "claude"}, {"skill", "--timeout", "0s"}} {
@@ -220,6 +220,8 @@ func TestSkillTargetFlagsAndRegistration(t *testing.T) {
 		force  bool
 	}{
 		{nil, ".agent", false}, {[]string{"--agent"}, ".agent", false}, {[]string{"--claude"}, ".claude", false},
+		{[]string{"codex"}, ".agents", false}, {[]string{"claude"}, ".claude", false}, {[]string{"agent"}, ".agent", false},
+		{[]string{"codex", "--force"}, ".agents", true}, {[]string{"--force", "claude"}, ".claude", true},
 		{[]string{"--claude", "--force"}, ".claude", true}, {[]string{"--force=false"}, ".agent", false},
 	} {
 		called := false
@@ -235,7 +237,8 @@ func TestSkillTargetFlagsAndRegistration(t *testing.T) {
 		}
 	}
 	for _, args := range [][]string{
-		{"--agent=false"}, {"--claude=false"}, {"--agent", "--claude"},
+		{"codex", "--agent"}, {"claude", "--claude"}, {"agent", "--online"}, {"codex", "--online"},
+		{"codex", "private-content"}, {"--agent=false"}, {"--claude=false"}, {"--agent", "--claude"},
 		{"--online", "--agent"}, {"--online", "--claude"}, {"--online", "--force"}, {"--online", "--force=false"},
 	} {
 		cmd := skillRoot(func(context.Context) ([]byte, error) { t.Fatal("invalid target fetched"); return nil, nil }, func(context.Context, []byte, string, bool) error { t.Fatal("invalid target installed"); return nil })